As part of the rapid growth of Internet and World Wide Web use, there has been an ever increasing growth in the availability of online services. Such online services include, for example, online banking, online email services, online picture sharing services, online dating services and online social networks. A single online service provider may provide a number of such services to online users. These services are, however, subject to fraud and abuse. For example, some users may sign up for online services using false information with the intent to misuse or abuse such services. For instance, someone may sign up for online email accounts and then use those accounts to generate and distribute unsolicited commercial emails, known as SPAM. In other cases, someone may use false information to sign up for an online service with the intent of distributing materials for which the particular online service is not intended. For example, someone may sign up with an online social networking service with the intent to use the social networking service to distribute commercial material. In some cases, such attempts to misuse or abuse online services is automated, where a computer program is used to sign up for such online services and carry out an improper use.
In order to reduce the amount of such fraud and/or abuse, online service providers may use a number of techniques. For instance, an online service provider may require that an individual attempting to sign up for an online service, or use a feature of an online service, perform an action that provides some level of confidence that the individual's intent is not to misuse the online service or services. For instance, to prevent fraud and/or misuse in the case of automated attempts to access, or use features of an online service, many online service providers use what is know as CAPTCHA technology, where a distorted series of characters is presented on a graphical interface and access to the service (or features of such services) is allowed only if the correct sequence of characters is entered by a user and returned to the online service provider's server that is monitoring access to the online services. A number of other techniques also exist for prevention of both automated and manual abuse. However, a drawback of current approaches is that they do not provide sufficient assurance that a user seeking to access an online service is who they claim to be. Additionally, abusers of online services often develop automated ways of circumventing fraud prevention techniques, such as CAPTCHA technology.